Resistance of acrylonitrile butadiene styrene polymers to discoloration



United States Patent 3,472,813 RESISTANCE 0F ACRYLONITRILE BUTADIENE STYRENE POLYMERS TO DISCOLORATION Arthur C. Hecker, Forest Hills, and Charles Abrarnotf,

Brooklyn, N.Y., assignors to Argus Chemical Corporation, Brooklyn, N.Y., a corporation of Delaware No Drawing. Filed Jan. 18, 1967, Ser. No. 610,003 Int. Cl. C08f 45/58 US. Cl. 26045.75 Claims ABSTRACT OF THE DISCLOSURE Stabilizer combinations are provided capable of enhancing the resistance of acrylonitrile butadiene styrene polymers to discoloration when heated at elevated temperatures of 300 to 375 F. or higher, composed of an alkyl polyphosphate salt and a polyhydric polycyclic phenol. The acrylonitrile butadiene styrene polymers having an enhanced resistance to heat deterioration are also claimed, as well as a process for stabilizing such polymers by incorporating therein combinations of alkyl fpolyphosphate salts and the polyhydric polycyclic phenols.

The alkyl polyphosphates have the formula:

wherein R R and R are inert substituents selected from the group consisting of hydrogen, halogen, and organic radicals containing from one to about thirty carbon atoms selected from the group consisting of alkyl, aryl, alkenyl, alkaryl, aralkyl, cycloalkenyl, cycloalkyl, alkoxy, aryloxy, acyl, carboxyl, and thiohydrocarbon groups,'Z is selected from the group consisting of oxygen, sulfur, alkylene, alkenylene, alicyclene, arylene, and mixed alkylenearylene and alkylene-alicyclene groups, m and m;, are integers from 1 to a maximum of 5, and m is an integer from 1 to a maximum of 4, x and x are integers from 0 to 4, and x is an integer from 0 to 3, y; is an integer from 0 to about 6, and y is an integer from 1 to about 5.

This invention relates to compositions useful in improving the resistance of acrylonitrile butadiene styrene polymers to discoloration upon exposure to heat at elevated temperatures, comprising a mixture of an alkyl polyphos- 3,472,813 Patented Oct. 14, 1969 phate salt and a polyhydric polycyclic phenol; to acrylonitrile butadiene styrene polymer compositions having an enhanced resistance to discoloration upon exposure to elevated temperatures, due to incorporation therein of such compounds; and to a process of enhancing the resistance of acrylonitrile butadiene styrene polymers to discoloration.

' Acrylonitrile butadiene styrene polymers, referred-to in the art and sold under the name ABS polymers, are known for their excellent combination of mechanical, thermal and electrical properties, as well as chemical resistance, and nontoxicity. In addition, ABS polymers are known for their ease of processing, low cost, and availability in a variety of grades which makes it useful in a variety of ways. For example, ABS polymer is available as molding powders, pellets, and extruded sheets which can be fashioned into telephones, pipes, automobile parts, shoe heels, golf club heads, molded helmets, carrying cases, molded cams, gears, furniture, knobs, handles, lawn mower wheels, other sporting goods, toys, electrical appliances, and many others. As conventionally produced ABS polymers are subject to discoloration when heated at elevated temperatures, that is, at temperatures sufficiently high to flux them, and especially at temperatures in excess of about 300 F. Thus, when ABS polymers are fabricated at such temperatures the polymers are often so badly discolored that they are commercially unacceptable, even when pigments such as titanium dioxide are added thereto. Titanium dioxide added to ABS polymer as a whitener therefor does hide the discoloration of the ABS polymer to some extent, but an off-tint can remain unless extremely large and uneconomical quantities are used.

A number of stabilizers have been proposed for stabilization of ABS polymers against discoloration. For example, US; Patent No. 3,267,069 to Cummings, dated Aug. 16, 1966, "suggests incorporating a mixture of zinc sulfide and an ester of thiodipropionic acid to inhibit discoloration and degradation of physical properties at elevated temperatures. Cummings discloses that his stabilizer combination can be employed with conventional stabilizers such as organic phosphites, polyhydric polycyclic phenols, and amine stabilizers.

US. Patent No. 3,244,668 to Knapp et al., dated Apr. 5, 1966, relates to the stabilization of plastics including styrene homopolymers and copolymers, such as polystyrene, and styrene-acrylonitrile copolymer; rubbery homopolymers of conjugated dienes; and rubbery copolymers of a conjugated diene and mono olefinic compound, employing a stabilizer system based on a combination of a side-chain-substituted cinnamic acid derivative of the type:

and a monocyclic hindered phenol of the type:

3 where Q is the aldehyde group (CHO) or the nitro group (N Three-component polymers such as ABS polymers are not disclosed. Knapp et al. indicates that among the stabilizers that can be employed in addition to the monocyclic phenols and cinnamic acid derivatives are salts of polyphosphoric acid partial esters.

US. Patent No. 2,499,503 to Hufi et al., dated Mar. 7, 1950, shows that the alkali metal penta-alkyl tripolyphosphates, such as pentasodium penta Z-ethylhexyl tripolyphosphate, members of the class mentioned by Knapp et. al., are stabilizers for polyvinyl chloride resins.

In accordance with the instant invention, a stabilizer system for acrylonitrile bntadiene styrene polymers (ABS polymers) is provided which enhances the resistance of ABS polymers to discoloration when heated at elevated temperatures. This combination consists essentially of an alkyl polyphosphate salt and a polyhydric polycyclic phenol. The phenol alone imparts improved but limited resistance, if any at all, to discoloration upon exposure to elevated temperatures. The polyphosphate alone does not noticeably improve the resistance of the ABS polymer to discoloration upon exposure to elevated temperatures. However, when the polyphosphate is used in combination with the phenol, the combination displays a surprising stabilizing action against discoloration indicating that the polyphosphate synergizes the stabilizing action of the phenol.

In addition, in accordance with the instant invention, ABS polymer compositions of improved resistance to discoloration due to exposure to elevated temperatures are provided consisting essentially of ABS polymer in combination with an alkyl polyphosphate salt, and a polyhydric polycyclic phenol.

Further, in accordance with the instant invention, a process for enhancing the resistance of ABS polymer to discoloration upon exposure to elevated temperatures is provided, which comprises incorporating in the ABS polymer an alkyl polyphosphate salt and a polyhydric polycyclic phenol.

The alkyl polyphosphate salts in accordance with the invention are defined by the following formula:

wherein M is a monovalent or bivalent metal cation or an ammonium, quaternary ammonium or organic amine cation; R is an alkyl radical having from one to about twenty-four carbon atoms; x is an integer from 2 to 4, representing the number of phosphorus atoms; n is an integer representing the number of M atoms, m is an integer representing the number of R groups, and z is an integer representing the number of (P O radicals, and is determined according to the valence of M. Accordingly, n is an integer within the range from 1 to z(valence of P O )m valence of M This group encompasses three principal subgenera of organometallic polyphosphates, the pyrophosphates, tripolyphosphates and tetrapolyphosphates.

Where M is monovalent, these polyphosphates take the following form:

Pyrophosphates:

(A) MR3P207 Tripolyphosphates:

Tetrapolyphosphates:

Where M is bivalent, these polyphosphates take the following form:

Pyrophosphates:

Tripolyphosphates:

(VII) n 12-2n( 4 13) 2 Tetrapolyphosphates:

M, R and n as used in the above formulae are the same as defined hereinbefore.

Typical metal cations (M) are, for example, sodium, potassium, lithium, barium, magnesium, strontium, calcium, tin, zinc, cadmium and nickel, and in addition, ammonium as well as organic amines, such as tri(tert-butyl)- amine, triethanolamine, diethanolamine, monoethanolamine, monoethanolamine, and quaternary bases such as tetramethyl ammonium hydroxide, and tetraethyl ammonium hydroxide.

Typical alkyl radicals (R) are, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, amyl, isoamyl, capryl, hexyl, heptyl, n-octyl, isooctyl, t-octyl, 2-ethylhexyl, nonyl, decyl, isodecyl, undecyl, dodecl, stearyl, palmityl, myristyl, and behenyl.

As exemplary of the polyphosphates which can be used, in addition to those given in the examples which follow, there can be mentioned pyrophosphates such as methyl trisodium pyrophosphate,

diethyl diammonium pyrophosphate,

butyl triammonium pyrophosphate,

diisoamyl dipotassium pyrophosphate,

dicapryl dilithium pyrophosphate,

dipropyl cadmium pyrophosphate,

di-Z-ethylhexyl barium pyrophosphate,

tetralauryl dizinic dipyrophosphate,

and hexastearyl calcium dipyrophosphate;

tripolyphosphates such as triethyl diammonium tripolyphosphate,

t-butyl tetrapotassium tripolyphosphate,

tetra-2-ethylhexyl sodium tripolyphosphate,

dicapryl tri-triethanolamino tripolyphosphate,

tridecyl disodium tripolyphosphate,

'monocapryl tetrasqdium tetrapolyphosphate,

hexaethyl tricadmium di-tetrapolyphosphate, tetra-Z-ethylhexyl tctrabarium di-tetrapolyphosphate, decastearyl calcium di-tetrapolyphosphate, decanonyl strontium di-tetraphosphate,

hexalauryl trinickel di-tetrapolyphosphate, and hexadodecyl trizinic di-tetrapolyphosphate.

The alkyl polyphosphate salt employed in the instant invention can be prepared by reacting in the presence of water phosphorus pentoxide, the desired aliphatic alcohol, and the desired metal oxide or hydroxide.

The following examples are illustrative of the preparation of several alkyl polyphosphates which can be employed in the instant invention.

EXAMPLE A Deca-2-ethylhexyl penta cadmium tetra tripolyphosphate was prepared as follows:

2-ethylhexanol (32.5 g., 0.25 mole) was added dropwise to phosphorus pentoxide (21.25 g., 0.15 mole, weighed under benzene) with stirring. The temperature of the mixture rose to 86 C. Thereafter, ca dmium oxide (16 g., 0.125 mole) and ml. water were added to this mixture during a 45 minute period.

The product formed was a white soapy mass which was dried on a steam bath for 8 hours and in a vacuum oven at a temperature of 60' to 80 C. for 14 hours. The dry product was a hard white solid which upon titration with ethylene diamine tetraacetic acid was found to contain 20.5% cadmium, which is the theoretical amount of cadmium contained in Cd (C H (P O EXAMPLE B Deca-2-ethylhexyl penta-barium tetra-tripolyphosphate was prepared as follows:

Z-ethylhexanol (32.5 g., 0.25 mole) was added dropwise with stirring to phosphorus pentoxide (21.25 g., 0.15

mole). The temperature of this mixture rose to about 86 C. Thereafter, barium hydroxide octahydrate (39.4 g., 0.125 mole) and 10 ml. water were added to this mixture during a 45 minute period.

The product obtanied was a white soapy mass which was dried on a steam bath for 8 hours and then a vacuum oven for 14 hours at a temperature of 60 to 80 C. The dry product obtained was a hard white solid which upon being titrated with perchloric acid in glacial acetic acid to a crystal violet end point was found to contain 27.25% barium. The theoretical amount of barium contained in Ba5(C H1q)1o(P O )4 is EXAMPLE C Pentastearyl penta-sodium di-tripolyphosphate was prepared as follows:

Phosphorus pentoxide (85 g., 0.6 mole weighed under benzene) was poured into a two liter 4-neck flask fitted with a heavy duty stirring motor. A mixture of alcohols (269 g.) containing a major portion of stearyl alcohol and having the following composition: 62.04% C18H3'10H, CH33OH, C14H29OH and C12H25OH, dissolved in benzene, was added dropwise to the phosphorus pentoxide with high speed agitation. Thereafter,

sodium hydroxide (40 g., 1.0 mole) dissolved in water (100 cc.) was added dropwise to the mixture of alcohol and phosphorus pentoxide.

The fluid product was poured into a stainless steel tray and evaporated on a steam bath, and then dried in a vacuum oven for 6 hours at a temperature of 70 to C.

The final product was an easily crushed white solid which was insoluble in water and which melted over a broad range and completely melted at 175 C. The actual yield of the product was about 379 g., which was 95.6% of the theoretical yield of pentastearyl penta-sodium ditripolyphosphate which is 397 g.

EXAMPLE D Penta-iso-tridecyl penta-sodium di-tripolyphosphate was prepared as follows:

Phosphorus pentoxide (85 g., 0.6 mole weighed under benzene) was added to a two liter 4-neck flask fitted with a heavy ,duty stirring motor. Iso-tridecyl alcohol (200 g.) dissolved in benzene was then added dropwise to the phosphorus pentoxide with high speed agitation. Sodium hydroxide (40 g., 1.0 mole) dissolved in water (100 cc.) was dropwise to the mixture of the iso-tridecyl alcohol and phosphorus pentoxide.

The fluid product was dried in a vacuum oven for 6 hours at C. The dry product was a waxy white solid which was soluble in water. The actual yield of the product was 91.8% of that theoretically expected for penta-isotridecyl penta-sodium di-tripolyphosphate.

EXAMPLE E (a) Penta-Z-ethylhexyl penta-sodium di-tripolyphosphate was prepared as follows:

Phosphorus pentoxide (42.5 g., 0.3 mole weighed under benzene) was added to a stirred mixture of 2-ethylhexanol (65 g., 0.5 mole) and sodium hydroxide (20 g., 0.5 mole) and water (20 g.). The temperature of this mixture rose from room temperature to 98 C. The product was dried in a vacuum oven for 6 hours at 90 C., resulting in a pasty solid which retained water and had a solids content of 81%. The sodium content of the 81% paste was found to be 5.61%. The theoretical amount of sodium contained in penta 2-ethylhexy1 pentasodium di-tripolyphosphite in an 81% paste is 6.94%.

(b) Pentasodium penta-Z-ethylhexyl di(tri-polyphosphate) was prepared in an alternate procedure as follows.

2-ethylhexanol (65 g.) was added during a 15 minute period to a stirred mixture of phosphorus pentoxide (42.5 g.) and hexane (100 ml.) in a 500 ml. tall form beaker. The temperature of the mixture rose to 72 C. Thereafter, sodium hydroxide (20 g.) in water (20 ml.) was slowly added to the mixture with stirring. The beaker containing the mixture was then heated for four hours on a steam bath and the mixture was dried in a vacuum oven at 82 C. for 8 hours.

The product obtained was a white rubbery solid which upon being titrated with perchloric acid was found to contain 8.56% sodium. The theoretical amount of sodium contained in penta-2-ethylhexyl penta-sodium di-tripolyphosphate is 9.79% sodium.

The polyhydric polycyclic phenols include aromatic nuclei which are linked by a polyvalent linking radical and are defined by the formula:

wherein Z is a polyvalent linking group selected from the group consisting of oxygen; sulfur; aliphatic, cycloaliphatic, and aromatic hydrocarbons; oxyhydrocarbon;

thiohydrocarbon; heterocyclic; carbonyl; sulfinyl; and sulfonyl groups, and has up to twenty carbon atoms.

Ar is a phenolic nucleus which can be a phenyl or a polycarbocyclic group having condensed or separate phenyl rings; each Ar group contains at least one free phenolic hydroxyl group up to a total of four (m and m =l to 4) Where R is aryl, alkyl or cycloalkyl, or thio-hydrocarbon groups having from one to about thirty carbon atoms, and carboxyl groups. Usually, however, each aromatic nucleus will not have more than about eighteen carbon atoms in any hydrocarbon substituent group. The Ar group can have from one to four substituent groups per nucleus.

Typical aromatic nuclei include phenyl, naphthyl, phenanthryl, triphenylenyl, anthracenyl, pyrenyl, chrysenyl, and fluorenyl groups.

The simplest form of polyhydric polycyclic phenol has the structure:

on on m wherein R R and R are inert substituent groups as set forth above, m and m are integers from one to a maximum of five, m is an integer from one to a maximum of four, x and x are integers from zero to four, and x is an integer from zero to three; y can be an integer from zero to about six and y can be an integer from one to five, preferably one or two.

Preferably, the hydroxyl groups are located ortho and/ or para to Z, and there is only one hydroxyl group per phenyl nucleus.

Exemplary Z groups are alkylene, alkylidene, alkenylene, arylalkylene, aralkylidene, cycloalkylene and cycloalkylidene, and oxaand thia-substituted such groups, carbonyl groups, tetrahydrofuranes, esters and triazino groups. The Z groups are usually bi-, tri-, or tetravalent, connecting two, three or four Ar groups. However, higher valence Z groups, connecting more than four Ar groups, can also be used. According to their constitution the Z groups can be assigned to subgenera as follows:

8 (1) Z groups made up of a single carbon carrying at least one hydrogen with other substituents linking two Ar nuclei, such as (2) Z groups made up of a single carbon carrying only substituents other than hydrogen, such as and (3) Z groups where at least two carbons connect the aromatic groups in an open-chain or cyclic arrangement, such as (4) Z groups where only atoms other than carbon link the aromatic rings, such as and ---(S),.

(5) Z groups made up of more than a single atom including both carbon and other atoms linking the aromatic nuclei, such as Although the relation of effectiveness to chemical structure is insufficiently understood, many of the most effective phenols have Z groups of subgenus 3, and accordingly this is preferred.

Exemplary polyhydric polycyclic phenols used in accordance with the instant invention are (3 -methyl-5-tert-b utyl-4-hydroxyphenyl (4-hydroxyphenyl) methane,

2,2'-methylenebis (4-methyl-5 -isopropylphenol) 2,2'-methylenebis 5 -tert-butyl-4-chlorophenol) (3 ,5 -di-tert-butyl-4-hydroxyphenyl) (4-hydroxyphenyl)methane,

(2-hydroxy-phenyl) (3 ',5 '-di-tert-butyl-4'-hydroxyphenyl) methane,

2,2'-ethylidenebis 4-octylphenol) 4,4-isopropylidenebis (Z-tert-butyl-phenol) 2,2-isobutylidenebis- (4-nonylphenyl) 2,4-bis( 4-hydroxy-3 -t-butylphenoxy -6- (n-o ctylthio)-l,3,5-triazine,

2,4,6-tris(4-hydroxy-3-t-butylphenoxy)-1,3,5-triazine,

2,2'-bis-(3-t-butyl-4-hydroxyphenyl)thiazolo- (5,4-d)thiazole,

2,2-bis (3 -methyl-5-t-butyl-4-hydroxyphenyl) thiazolo-(5,4-d)-thiazole,

4,4'-bis(4-hydroxyphenyl)pentanoic acid octadecyl ester,

cyclopentylidene 4,4'-bisphenol,

2-e-thylbutylidene 4,4'-bisphenol,

4,4'-cyclooctylidenebis (2-cyclohexylphenol) [3,5-thiodiethanolbis(3-tert-butyl-4-hydroxyphenoxy acetate),

1,4-butanediolbis(3-tert-buty1-4-hydroxyphenoxy acetate),

pentaerythritoltetra(4-hydroxyphenol propionate),

2,4,4'-tri-hydroxy benzophenone,

bis(2-tert-butyl-3-hydroxy-5-methylphenyl) sulfide bis(2-tert-butyl-4-hydroxy-5-methylphenyl) sulfide,

bis(2-tert-butyl-4-hydroxy-S-methylphenyl) sulfoxide,

bis(3-methyl-5-tert-butyl-4-hydroxy benzyl) sulfide,

bis(2-hydroxy-4-methyl-6-tert-butyl phenyl) sulfide,

4,4-bis(4-hydroxyphenyl) pentanoic acid octadecyl thioprionate ester,

1,l,3-tris(2'-methyl-4'-hydroxy-5-tert-butylphenyl) butane,

1,1,3 -t1'is 1-methyl-3 -hydroxy-4-tert-butylphenyl) butane,

1, 8-bis (2-hydroxy-5-methylbenzoyl) -n-octane,

2,2-methylene-bis [4'- (3 -tert-butyl-4-hy droxyphenyl thiazole],

l-methyl-3-(3-methyl-5-tert-butyl-4-hydroxybenzyl) naphthalene,

2,2'-(2-butene)bis(4-methoxy-6-tert-butyl phenol).

The polyhydric polycyclic phenols used in the invention can also include condensation products of phenol or alkyl phenols with aldehydes, for example, formaldehyde, acetaldehyde, and propionaldehyde, or with ketones, for example, acetone.

The polyhydric polycylic phenols used in the invention can also be condensation products of phenol or alkylphenols with hydrocarbons having a bicyclic ring structure and a double bond or two or more double bonds, such as wpinene, fi-pinene, dipentene, limonene, vinylcyclohexene, dicyclopentadiene, alloocimene, isoprene, and butadiene. These condensation products are usually obtained under acidic conditions in the form of more or less complex mixtures of monomeric and polymeric compounds. However, it is usually not necessary to isolate the individual constituents. The entire reaction product, merely freed from the acidic condensation cataylst and unchanged starting material, can be used with excellent results while the exact structure of these phenolic condensation products is uncertain, the Z group linking the phenolic muclei all falls into the preferred subgenus 3. For methods of preparation see e.g. US. Patent No. 3,124,555, US. Patent No. 3,242,135, British Patent No. 961,504.

A sufiicient amount of the stabilizer combination of the invention is used to enhance the resistance of the ABS polymer against discoloration upon exposure to elevated temperatures. Small amounts are susally adequate. Amounts within the range from about 0.1 to about 10% total stabilizers by weight of the ABS polymer are satisfactory. Preferably, from about 0.25 to about 2% is employed for optimum stabilization. Amounts of the polyphosphate within the range from about 0.05 to about 5% by weight of the ABS polymer and amounts of the polyhydric polycyclic phenol Within the range from about 0.05 to about 5% by weight of the ABS polymer are satisfactory. Preferably, from about 0.25 to about 2% of the polyphosphate and from about 0.25% to 2% of the polyhydric polycylic phenol are employed, for optimum enhancement of resistance to discoloration.

The stabilizer combination of the invention generally contains from about to about 50 parts of polyphosphate and from about 10 to about 50 parts of the polyhydric plycyclic phenol, by weight of the combination.

The stabilizer composition can be formed by simply mixing the individual ingredients in the dry state or in a suitable liquid medium. It is frequently helpful to combine the phenol with the freshly prepared polyphosphate salt in the presence of the solvent and water in which the salt has been prepared before the solvent and water are finally removed. Another helpful expedient is to prepare the stabilizer composition in the form of an aqueous emulsion. Such an emulsion can be added to a freshly made ABS polymer latex before the polymer is isolated from the latex by the usual procedures of coagulation or spray-drying. A masterbatch technique can be utilized to provide both wet and dry combinations of the stabilizer composition with the ABS polymer in proportions for compounding into larger quantities of polymer to be stabilized.

In addition to the polyphosphate and phenol, other thermal antioxidants and light stabilizers can be employed in the compositions of the present invention, such as organic phosphites as set out in U.S. Patent No. 3,244,650 to Hecker et al., dated Apr. 5, 1966, the organic phosphites having the formula (RA) P in which A can be oxygen or sulfur or a mixture of the same, and R can be selected from the group consisting of aryl, alkyl, cycloalkyl, aralkyl and alkaryl groups, in any combinations, and esters of thiodipropionic acid as set out in U.S. Patent No. 3,255,136 to Hecker et al., dated June 7, 1966.

ABS polymers are conventionally blended with additives such as fillers, pigments and lubricants. Appropriate pigments and fillers are, for example, flour, cotton, shredded or chopped cloth, talc, chopped canvas, paper pulp forms, asbestos, powdered mica, calcium carbonate, carbon, graphite, quartz, diatomaceous earth silica, fibrous glass, barytes, calcium silicate, iron, barium sulfate, litharge, clay and titanium dioxide. Fillers are normally used in an amount of from about 2 to about 40% by weight of the polymer. Typical lubricants are mineral oil, natural and synthetic waxes, fatty acids such as stearic acid, alkaline earth and heavy metal stearates, and aliphatic alcohols, ketones, and epoxides having from about 16 to about 60 carbon atoms in the molecule, including stearyl alcohol, palmitone, behenone, oleone, cetyl palmitate, 1,2-epoxydocosane, and isooctyl epoxystearate, in amounts of from about 0.2 to 3% of the polymer.

If a combination of stabilizers is to be used, it may be formulated as a simple mixture for incorporation in the ABS polymer by the polymer manufacturer or by the converter. An inert organic solvent such as xylene, cyclohexanone, ethyl benzene and the like can be used to facilitate handling, if the ingredients do not form a homoan elastomeric substrate, such as polybutadiene. The contribution of the acrylonitrile, styrene and butadiene is each important. Terpolymers of the three monomers do not always have the desired properties, and ABS graft copolymers are most common, and include a styrene acrylonitrile copolymer phase and a preformed polybutadiene substrate on which is grafted styrene and acrylonitrile, usually by emulsion, bulk or suspension polyemrization. See Chemistry and Industry, Aug. 13, 1966, pages 1399-1405. All of these are encompassed herein under the terms acrylonitrile butadiene styrene polymer, or ABS polymer.

ABS polymers generally contain from about 15 to about 35% acrylonitrile, from about 5 to about 35% butadiene, and from about 40 to about styrene, by weight. The matrix usually has a molecular weight of from about 200,000 to about 450,000 or more, and a density of from about 0.99 to about 1.09.

The acrylonitrile portion of the ABS polymer imparts chemical resistance to the polymer; the styrene portion of the ABS polymer imparts good fabrication characteristics to the polymer; and the rubber or butadiene portion of the ABS polymer provides the rubberiness and toughness to the olymer. Accordingly, chemical resistance, good fabrication characteristics, and rubberiness and toughness features can be varied in any given ABS polymer by varying the quantities of the acrylonitrile, butadiene and styrene. For example, the impact strength of the ABS polymer can be increased by increasing the amount of butadiene in the polymer. However, increase in impact strength is accompanied by slight reduction in heat resistance, rigidity, electrical properties and some of the other strength properties.

Heat resistant properties of the ABS polymer can be improved by increasing the amount of acrylonitrile in the polymer. However, increased heat resistance, such as increasingly high heat-distortion temperatures, usually is accompanied by decreased impact strength, especially at low temperatures. Increasingly good fabrication characteristics of the polymer is obtained where larger quantities of styrene are used. However, such an ABS polymer usually has lower impact strength. Accordingly, the impact strength of ABS polymer at 73 F. varies from 9 ft.-lb./ in. notch in extra high and low temperature impact grades, to 1.5 for medium impact grades.

The tensile strength of ABS polymer varies from 8800 p.s.i. for medium impact grades, with a tensile modulus of 400,000 to as low a tensile strength as 2400 p.s.i., for a semi-flexible extrusion grade, and a tensile modulus of 2,100,000. The hardness of ABS polymer ranges from a Rockwell 118 for medium impact grade to a Rockwell 62 for a low temperature grade material. The range of deflection temperature for ABS polymer is from 230 F. at 264 p.s.i. and 240 F. at 66 p.s.i., respectively, for heat resistant grades, to as low as F. at 264 p.s.i. and 202 F. at 66 p.s.i., respectively, with most commercial grades falling in the upper end of the range.

ABS polymer can be prepared by polymerizing acrylonitrile monomer and styrene monomer in a previously prepared polybutadiene latex, or butadiene copolymer rubber latex, under such conditions than an appreciable portion of the acrylonitrile and styrene become grafted or polymerized directly on the polybutadiene molecules. The polybutadiene portion or base portion of the ABS graft polymer molecule is rubbery, while the acrylonitrile and styrene grafted comonomer portions of the graft polymer molecule are resinous. See U.S. Patent No. 2,820,773, dated Jan. 21, 1958, to Childers and Fisk for a detailed description of the graft polymerization technique for forming ABS polymer.

ABS polymer can also be prepared by blending styreneacrylonitrile copolymer resins with butadiene-based elastomers, such as is described in U.S. Patent No. 2,439,- 902, dated Apr. 6, 1948 to Daly, and No. 2,600,024, dated June 10, 1952 to Romeyn et al.

In addition, ABS graft copolymer can be physically blended with additional quantities of separately prepared resin, for example, styrene-acrylonitrile resin, with or without additional separately prepared butadiene-acrylonitrile copolymer rubber. See U.S. Patent No. 2,802,808 dated Aug. 13, 1957 to Hayes for a complete description of the preparation of ABS polymer from ternary blends containing a resin, for example, a copolymer of styrene of a-methylstyrene with acrylonitrile or methacrylonitn'le, a rubber (polybutadiene or butadiene copolymer), and a graft copolymer of styrene-acrylonitrile and butadiene.

Mixtures of ABS polymers with other compatible polymers, (for example, the polycarbonate of 4,4-isopropylidene-bisphenol) and copolymers of acrylonitrile, or

nitrile-styrene, butadiene-styrene, and butadiene-acrylonitrile rubber, the ABS polymer being present in a sufiicient amount, usually a major amount, that is, about 85% by weight or more to present the stabilization problem resolved by the invention, can also be stabilized.

Furthermore, the styrene monomer of the ABS polymer can be replaced in whole or in part by a-methylstyrene in order to improve the heat distortion temperatures of the ABS polymer. Similarly, methyl methacrylate can be used in place of some of the acrylonitrile.

All of the above polymers fall within the term ABS polymer, as used herein.

Typical available ABS polymers and their physical properties are:

methacrylonitrile, butadiene, and styrene, such as acrylo- 15 TABLE A Cycolac ABS Polymers Grade and Characteristics GS T X-27 X17 X-7 Maximum toughness with high Maximum modulus, Maximum high heat GSM high heat with good High heat injection Toughness with high moldwith and blow with modulus, ability, toughness, PROPERTIES-Reported values pertain molding, high flow, injection injection injection only to natural resins; pigmenting may ASTM test GS iniection molding, molding, molding, vary the properties Condition Units Method extrusion molding extrusion extrusion extrusion MECHANICAL:

Izod impact strength, unnotched- 73 F. Ft m m 29. 3 26. 33. 0 32. 0 bar 1 notched 73 F. 6. 2 5. a a. 1 2. 5 4. 2 K F g 2.6 2.1 1.3 1,4 7 F 2. 1 1. 8 1. 0 0. 7 1. 2 Charpy impact strength, unnotched. 73 F. 35. 0 26. 0 19. 3 33. 0 M" bar notched 73 F. d0 D-256-56 4. 7 3. 7 1. 9 3. 1 --20 F. Method 2. 0 2. 1 1. 1 1.1 -20 F. B. 2. 2 1. 7 0. 9 1. 4

Tensile stren th T e 1 thickness 160 F. 3 400 3,200 4,600 4,000 1, g yp }P- a gfig g' 51000 0,000 7, 300 1,200 e, 000 -40 F. 9, 200 9, 500 11, 500 10, 400

Tenfile modulus, Type I, M" thickness 73 F P.5d- Db-fiziigl-iii T, 310, 000 300, 000 390, 000 380, 000 330, 000

a mm.

Flixumlsmngth x x bar 2g: P.s.i D79061, No failure No failure No failure No failure No failure 0 0.05/mi.n. -40 F.

Flexural eld stren th %"x 1" x4"bar 160 F. 5, 700 5, 500 7, 500 6 800 6, 200 1 yi g 73 RF figif' 9, 700 9, 600 11,800 10, 600 10,200 -40 F. 15, 200 15, 100 18, 800 18, 100 16, 100

Flexural modulus, x 1" X 4 bar 1 160 F. 220,000 210, 000 310, 000 270, 000 260, 000 0 73 F.} ggigk 320, 000 320, 000 400, 000 380,000 300, 000 40 F. 360, 000 360, 000 460, 000 420, 000 390, 000

Hardness, y," thickness 73 F. Rockwell R.-- D-785-62, 103 104 112 110 107 Method A.

Wearindex,Taber,Volumelossmethod, 73 F., Percent 19.2 18. 8 19. 0

08-17 wheel, 1,000 g. weight. R.H. Deformation under load 24 hr., 122 F., Percent D62i59 0. 52 0. 53 0. 21 0. 36

2,000 p.s.i.

THERMAL:

Coeificient of linear thermal expansion In.lin./ C D-698-44. 9. 5 10- 9. 5 10- 6. 0X10" 6. 2x10 8. 2X10- In./in.IF Calculated 5. 3X10- 5. 3X10- 3. 3X10" 4. 5X10- Deflection temperature unannealed, 264 p.s.i. o F at 10 mils D 193 192 226 220 203 x x 5" bar 1 66 .S.i 211 209 238 220 ya x Zero load 221 250 250 230 Deflection temperature annealed, 264 p.s.i. 218 215 244 238 224 $6" x y," x 5" bar 66 13.5.1. do D64856-. 224 221 249 230 Zero load 229 226 254 235 Thermal conductivity- B.t.u.lhr.lit. l 1. 1. 54 2. 1.

F. in. 5. 45X10- 5. 30X10- 8 18Xl0- 6 52X10- CaI./sec./ 0477-45.-.. cmfl/ 0.! cm.

Flammability, W x 34" x 5" bar In./min D03563.-.. 1. 5 1. 5 1. 8 1.4

See footnotes at end of table.

TABLE AContinued Cycolac ABS Polymers Grade and Characteristics GS T X27 X-17 X-7 Maximum toughness with high Maximum modulus, Maximum high heat GSM high heat with good High heat injection Toughness with high moldwith and blow with modulus, ability, toughness, PROPERTIES-Reported values pertain molding, high flow, injection injection injection only to natural resins; pigmenting may ASTM test GSE injection molding, molding, molding, vary the properties Condition Units Method extrusion molding extrusion extrusion extrusion ANALYTICAL:

Specific gravity 73 F D-792-60'I, 1. 04 1. 04 1. 06 1. O6 1. 05

Method A.

Water absorption 73 F. Percent D57063 0. 43 0. 40 0. 36 0. 43

Mold shrinkage In./in D95551. 0. 006 0. 005 0. 004 0. 004 0. 005

Cycolac ABS Polymers Cycolon medium impact ABS Special polymers ABS resins Grade and Characteristics H L C G E A AH DH EP-3510 Good tough- Very high Grey only, Good ness at impact at for chrome toughlow Toughlow AM for plated, ness, temp., ness with temp., injection High High parts PROPERTIES-Reported values pertain injection injection low injection molding, heat, heat, in ection only to natural resins; pigmenting may molding, molding, gloss, molding AE for injection injection molding vary the properties extrusion extrusion extrusion extrusion extrusion molding molding extrusion MECHANICAL:

Izod impact strength, unnotched- N break No break No break No break 23. 0 18. 3 15.0 26. 0 3 bar notched 6. 3 6. 7 8.0 8. 5 4. 0 4. 0 3. 5 4. 5 2.8 4.3 1.4 1.4 1.2 1.4 2.6 3.8 2.0 3.0 1.0 1.0 0.8 1.0

Charpy impact strength, unnotched No break N 0 break 19. 0 26. 0 34, bar notched 5. 3 6. 0 2. 6 3. 7 2. 9 3. 7 1. 5 1. 6 2. 6 3. 1 1. 2 1. 5

Tensile strength, Type 1, hi thickness 2, 400 2, 600 3, 500 H... 3, 200 4, 700 5, 000 6, 300 6, 000 7, 200 7, 400 10, 000 9, 500

Tensile modulus, Type I, thickness 230, 000 230, 000 260, 000 230, 000 330, 000 350, 000 380,000 310, 000

Flexural strength, 56" x 1 x 4 bar No failure No failure No failure No failure No failure No failure Flexural yield strength, 56 x 1 x 4 bar 4, 100 4, 300 3, 500 5, 400 6, 800 7, 700 5, 500 7, 600 7, 800 7, 200 7, 300 9, 900 11, 000 11, 800 9, 200 11, 800 12, 100 10, 500 17, 300 17, 500 18, 100 15, 100

FleXllral modulus, 56" x 1" x 4" bar 160, 000 160,000 140, 000 240, 000 250, 000 300,000 210, 000 240, 000 250, 000 260, 000 230, 000 260, 000 370, 000 400, 000 330, 000 280, 000 180, 000 300, 000 420, 000 410, 000 440, 000 360, 000

" Hardness, i4" thickness 88 so as 85 s 103 112 104 Wear index, Taber, Volume loss method, CS-l? wheel, 1,000 g. weight 22. 7 23. 0

Deformation under load 1. 22 1. 12

THE RMAL:

Coeificient of linear thermal expansion 10. 41X10- 10. 1 10- 8. 3X10- 8. 5X10 7. 2X10 9- 5X1 Dgflec(ti)on temperature, unannealed, M x V 5" Deflection temperature annealed V x V" x 5" bar -l 214 218 199 221 223 215 222 224 211 223 227 221 228 227 220 227 232 226 Thermal conductivity 1. 56 1. 56 1. 54 j 5. 05x10 5. 05x10 5. X10- 4 Flammability, x x 5" bar 1. 4 1. 4 1. 6 1. 6 1. 6 1. 5

" ANALYTICAL:

' Specific gravity 1. 02 1.02 1. 04 1. 02 '1. 05 1. e4 1. 05 1. 07

Water absorption 0. 42 0. 0. 40 0. 33 0. 32 0. 40

'- Mold shrinkage 0. 007 0. 007 0. 005 0. 004 0. 004 0.005

1 Compression molded 2 Injection molded ASTM D1130-T Conditioned by ASTM 13618-61 The stabilizer is incorporated in the ABS polymer in suitable mixing equipment, such as a mill, a Banbury mixer, an extruder, and the like.

The stabilized ABS polymer can be worked into the desired shape, such as by milling, calendaring, extrusion or injection molding or fiber molding.

The following examples in the opinion of the inventors represent the best embodiments of their invention.

In the examples, the ABS polymer used was Cycolac T, a polymer of a mixture composed of 27% acrylonitrile, 20% butadiene, and 53% styrene. The two-component stabilizer system of the invention was evaluated against the stabilizing eifect of each component thereof, taken singly. The ABS polymer was pigmented by adding parts of titanium dioxide to each 100 parts of the polymer, thus giving the unstabilized ABS polymer a creamy white initial color. The stabilizers being tested were Weighed and dispersed in the unstabilized ABS polymer on a two-roll laboratory mill, and fluxed at a temperature of 280 to 300 F. for two to three minutes. The milled sheets were smooth and had dull surfaces. The sheets were then tested for resistance to deterioration when heated, by one or more of the following tests.

Oven aging at 350 F. and 375 F.

The ABS polymer strips cut from the milled sheets were heated in a circulating air oven at temperatures of 350 F. for two hours. Samples were withdrawn at 15 minute intervals and examined for discoloration. The discoloration was then rated visually by color, and numerically by color number, according to the following standard color scale, based on an oven test of a standard polymer heated at 350 F. for three hours:

COLOR NUMBER SCALE however applied when the sample is heated at I other temperatures, such as 375 F., comparing the sample against the standard at 350 F. A higher temperature is more rigorous, with the result that the color of the polymer may deteriorate two color numbers or more in each heating period.

Compression molding and oven aging Pieces cut from several milled sheets of ABS polymer, each containing a difierent stabilizer system were placed side by side in a mold and compression molded at 375 F. for five minutes to give 6 by 6 inch slabs, mils thick, With a glossy surface. Clear demarcation lines were noted between different samples. The whole slabs were aged in a circulating air Oven, and strips including a part of each sample were cut ofi at 15 minute intervals. The colors of the samples were rated and recorded as described.

Mold stability test in absence of air Pieces cut from several milled sheets of ABS polymer, each containing a diiferent stabilizer or stabilizer combination, were compression molded at 375 F. for varying periods of time. The resulting 6 x 6 x 0.04 inch slabs had a glossy surface and clear demarcation lines between different samples. Sufficient materialwas placed in the mold to assure some excess over the quantity required to till the mold completely. The excess was squeezed out as the plastic began to flow and this displacement of plasticalso served to assure that any air originally present in the mold was displaced. The colors of the samples after molding for the desired time were rated and recorded as described.

Time of Heatin at 350 F. Color (minutes) Number Stages of Noticeable Difference in Color Heating period:

The above table is based on the color change of a nonstabilized standard polymer which develops a further noticeably intensified discoloration in each fifteen minute heating period when heated at 350 F. A polymer sample having improved resistance to discoloration when heated will not develop a noticeably different discoloration in each heating period, but will discolor more slowly, if at all, and will tend to retain a given color over one or more heating periods. Thus, a relatively stable sample after sixty to ninety minutes of heating may well retain a color number maximum of 2 or 3, as compared to 4 to 8 for the standard sample. Thus, the color number is a direct measure of the heat stability, vis-a-vis the color standard.

The color number is based on color change when the standard is heated at 350 F. The color numbers are EXAMPLES 1 TO 3 An alkyl polyphosphate-polyhydric polycyclic phenol stabilizer system of the invention was evaluated against the stabilizing effect of the components thereof, taken singly. The stabilizers used were penta-Z-ethylhexylpenta-sodium di-tripolyphosphate and l,4bis(2-hydroxy- 3-t-butyl- 5' -methylphenyl) 2-butene together with its polymer (Phenol A). In each case, to obtain results based on equal stabilizer concentration, a total of 1 part of stabilizer per 100 parts of ABS polymer was used. Test samples were prepared as described hereinbefore. Tables LA and LB below set out the parts of polyphosphate and phenol stabilizer in each system per 100 parts of ABS polymer, and the test results obtained after oven-aging at 350 'F. and 375 F., respectively.

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355353 3 0 mo unuwummow bomb: on o 530% EXAMPLE 13 The stabilizer system of the invention was evaluated against the stabilizing effect of the various components thereof individually, employing 0.6 part of stabilizer in each sample. Composition of the samples and results obtained in compression molding the milled sheets at 375 F. in the absence of air for 5, 30 and 60 minutes are shown in Table VIII.

total valence of the z(P O radicals; and a polyhydric polycyclic phenol having the formula:

(m (0mm,

(R011 ah, yr 3);; yr

wherein R R and R are inert substituents selected from the group consisting of hydrogen, halogen, and organic radicals containing from one to about thirty carbon atoms selected from the group consisting of alkyl, aryl, alkenyl,

TABLE VIII.COMPRESSION MOLDING AT 375 F.

Amount Example No. Stabilizer System (part) Milled Sheet Molded, 5 min. Molded, min. Molded, min.

Control 1 N0 stabilizer 0 Beige. Control 10 PhenolA 0.6 0 3.

Creamy white. Grayish beige.-. Graylsh beige. Grayish beige. Control 11 Sodium 2-ethylhexyl polyphosphate...-. 0. 6 0 1 2 2.

Creamy white. Pale beige Example 13 Phenol A -3 0 0 0l Sodium 2-ethylhexyl polyphosphate 0.3 Creamy white- Creamy white- Very pale beige 1 Control 10 rated by comparison with Control 1.

In the absence of air, all samples discolored less than in the presence of air. In the absence of air, the sample containing only the phenol was poorer than an unstabllized sample. The stabilizer combination of Example 13 provided good protection and a substantial improvement over the next best formulation (unstabilized or polyphosphate alone), whether the molding cycle was short (5 minutes) or as long as 60 minutes at 375 F.

Further appreciation of the effectiveness of the stabilizer combination can be gained by considering the effectiveness of stabilizers in the presence and absence of air. These conditions in actual practice are not alternatives, but can occur successively on a single sample:

Having'regard to the foregoing disclosure, the following is claimed as the inventive and patentable embodiments thereof:

1. A stabilizer combination capable of enhancing the resistance of acrylonitrile butadiene styrene polymers to deterioration when heated at 350 C., consisting essentially of an alkyl polyphosphate salt having the formula: M R (P O;., wherein M is selected from the group consisting of alkali metal, alkaline earth metal, tin, zinc, cadmium, nickel, ammonium, quaternary ammonium, and organic amine cations, R is an alkyl radical having from one to about twenty-four carbon atoms, x is an integer from 2 to 4, z is the number of (P O radicals, and is an integer from 1 to n(valence of metal)+m valence of polyphosphate group n is the number of M cations, and is an integer from 1 to z(valence of polyphosphate group)m valence of metal alkaryl, aralkyl, cycloalkenyl, cycloalkyl, alkoxy, aryloxy, acyl, carboxyl, and thiohydrocarbon groups, Z is selected from the group consisting of oxygen, sulfur, alkylene, alkenylene, alicyclene, arylene, and mixed alkylene-arylene and alkylene-alicyclene groups, m and m are integers from 1 to a maximum of 5, and m is an integer from 1 to a maximum of 4, x and x are integers from 0 to 4, and x is an integer from 0 to 3, y is an integer from 0 to about 6, and y is an integer from 1 to about 5, the polyphosphate being present in an amount to enhance the stabilizing effectiveness of the phenol.

2. A stabilizer combination in accordance with claim 1 wherein the alkyl polyphosphate salt is an alkali metal salt.

3. A stabilizer combination in accordance with claim 1 wherein the alkyl polyphosphate is an alkaline earth metal salt.

4. A stabilizer combination in accordance with claim 1 wllierein the alkyl polyphosphate salt is an ammonium sa t.

5. A stabilizer combination in accordance with claim 1 wherein the alkyl polyphosphate salt is an amine salt.

6. A stabilizer combination in accordance with claim 1 wherein the alkyl polyphosphate salt is a cadmium salt.

7. A stabilizer combination in accordance with claim 1 wherein the alkyl polyphosphate salt is a nickel salt.

8. A stabilizer combination in accordance with claim v1 wherein the alkyl polyphosphate salt is a zinc salt.

9. A stabilizer combination in accordance with claim 1 wherein Zis sulfur.

10. A stabilizer combination in accordance with claim 1 wherein Z is alkylene.

11. A stabilizer combination in accordance with claim 1 wherein Z is alkenylene.

12. A stabilizer combination in accordance with claim 1 wherein R R and R are alkyl substituents.

13. An acrylonitrile butadiene styrene polymer, having its resistance to deterioration when heated at 300 F and above enhanced by an amount within the range from about 0.1 to about 10% by weight of the polymer of a stabilizer combination in accordance with claim 1.

14. An acrylonitrile butadiene styrene polymer in accordance with claim 13, in which the amount of polyphosphate is within the range from about 0.05 to about 5% and the amount of polycyclic polyhydric phenol is within the range from about 0.05 to about 5%.

binations.

References Cited UNITED STATES PATENTS Hulf et a1, 260-45.7 Serdynsky et a1 260-45.7 Costa et a1 260-45.7 Hunter 260-45.7 Havens 260-45.7

Jankowiak 260-45.7

30 Havens 26045.7 Jankens 260-4-5.7 White 260-45.7 Spacht 26045.95 Cofiield 260-881 Hecker et a1. 26045.95 Knapp et a1 260-45.85 Cummings 260-45.75 Bawn 260-45.75

DONALD E. CZAJA, Primary Examiner V. P. HOKE, Assistant Examiner US. Cl. X.R. 

